1. Field of the Invention
This application relates to apparatus for releasably driving a winch. More particularly a crank handle is described for driving winches of the kind used on sailing vessels. The crank having a releasable locking mechanism at the interface between crank and winch that allows one handed removal of the crank from the winch.
2. Brief Description Of Related Developments
Winches are generally constructed having a drum that is mounted on a platform for rotation about an axis. The drum is driven by engagement with a crank arm that extends transverse to the axis to provide a mechanical advantage. Such crank and winch devices are well known. In use a rope or line to be hauled is wrapped several turns about the drum and the drum is driven in rotation by manual operation of the crank arm. Rotation of the drum causes the line to be drawn in by further wrapping the line about the drum.
Sailboats (usually of length greater than 25 feet) typically employ the use of winches to control the lines (“sheets”) that are attached to the sails. These winches are usually deck mounted and operated by means of a crank handle. The winch drum is constructed with an axially aligned socket having an octagonal cross section. A male drive head is constructed on the crank with a matching octagonal cross section. The drive head of the crank fits into the octagonal socket, generally located at the top of the winch drum. Winch cranks come in a wide variety of shapes, sizes, and construction material, but share the common octagonal shape and size of the drive, which fits into the winch itself.
In operation the crank is engaged in the drum and cranked in a circular motion. If a line has been wrapped around the winch drum, this circular motion turns the drum and causes the line to be hauled in. In applications for marine and sailing use, the crank is generally designed to be removed from the drum when not being cranked. This requires a releasable locking mechanism to prevent the crank from becoming dislodged. More often than not, this results in the handle being lost overboard.
A crank, typical of those currently used, is shown in FIG. 1. The locking mechanism of this prior art crank handle consists of a square plate located at the bottom of the drive head. The locking plate is mounted on a shaft that extends through a bore in the drive head of the crank arm. The shaft is allowed to rotate thereby, moving the plate from alignment with the octagonal cross section to a position in which it interferes with a shoulder at the bottom of the drive socket within the winch body. The rotation of the locking plate is accomplished by means of a small finger lever located at the top of the locking plate shaft. In general the locking plate shaft is spring biased in the locked position and therefore must be rotated into alignment in order to attach or release the crank. Not all crank handles in use today are the locking type. Those that are, however, generally employ this type of locking mechanism. Another prior art locking mechanism is shown in U.S. Pat. No. 6,491,285.
While effective, this rotating locking plate is fully exposed and is often damaged as the winch handle is repeatedly engaged or disengaged from the winch. This is especially true in the case of sailboat racing where frequent (often abusive) use of the crank is common. Damage to the locking plate can result in the winch handle becoming captured within the winch making it difficult or impossible to release.
As shown in FIG. 9, the drive head of the prior art presents a flat surface 50 to the socket opening having an octagonal cross section. Therefore, it is necessary to align the mating profiles with some precision. This creates an inherent difficulty in aligning the female and male parts of the winch and drive head, especially as a sailing vessel, rolls, pitches, and yaws under sail. In is an object of this invention to facilitate the engagement of the drive head in the socket.
Another disadvantage of crank handles using the locking plate type of mechanism is that it generally requires the use of both hands to engage or disengage the handle. While it is possible to release the handle with one hand using the thumb to unlock, this may be awkward because of the length of the crank arm. In practice both hands are commonly used to accomplish this task. Typically, one hand is used to operate the finger lever, while the other hand is used to pull the handle upward to free it from the winch drum. Given the three-directional movement of a sailboat underway, using both hands to attend any piece of equipment is inconvenient and often dangerous. This is especially true in a race situation where accurate and timely executions of sail trim actions are critical.
It is a purpose of this invention to provide a mechanism for reliably locking and releasing the drive head of a crank. It is also a purpose of this invention that the engagement and release operation can be accomplished with one hand.